Compartmented envelopes are well known in the art. They are generally used for mailing two different items or sets of items within the same envelope. For instance, banks use compartmented envelopes for mailing canceled checks and bank statements to their customers. Moreover, such envelopes usually include a window for one of the compartments whereby a preaddressed item can be accomodated thereby obviating the need to address the envelopes either before or after stuffing. In this regard, particular care must be exercised when a preaddressed item smaller than the envelope itself is inserted to insure that the address lines up with and stays behind the window. Compartmented envelopes are also useful for incorporating both first and third class matter together where a suitable opening is incorporated in the envelope structure to permit postal inspection.
The following prior art patents are believed to be exemplary of the type of envelope disclosed herein.
U.S. Pat. No. 2,200,099 Prentice PA1 U.S. Pat. No. 2,944,728 Whitman PA1 U.S. Pat. No. 3,136,476 Berkowitz PA1 U.S. Pat. No. 3,140,817 Fitzgerald PA1 U.S. Pat. No. 3,266,712 McCleneghan
The patent to Prentice shows an envelope blank structure substantially as disclosed herein. The Prentice structure is used exclusively for incorporating both first and third class matter in the same envelope and does not encompass the herein disclosed two compartment structure, document locking feature and windowed construction. Meanwhile, the patents to Whitman, Berkowitz, Fitzgerald and McCleneghan each disclose compartmented envelopes, with means for providing a separate compartment for items smaller than the envelope itself, but with constructions that are more complex and which use more paper than the construction disclosed herein. Furthermore, none of the latter patents disclose an embodiment that may be used for both first and third class mail. Accordingly, the present invention distinguishes over the prior art because of its simplicity, multiple use capability and economical construction wherein a document locking feature is provided within the compartmented envelope structure with the aid of pressure sensitive adhesive applied to at least one of the elongated end closure flaps of the envelope.